Billions of tonnes of materials are transferred by conveyor every year and most of this needs to be sampled for quality control, plant regulation, or for checking that sales obligations are met. In many instances, the mass of this material must also be accurately measured.
Falling-stream samplers are the most accurate way to sample the material on a conveyor belt but these samplers are difficult to retrofit to existing conveyor belt situations and often have access and availability problems.
Cross-belt samplers are a much cheaper alternative to retrofit, and are often installed in new plant, but are not as accurate as falling-stream samplers.
Weightometers are often placed under belt conveyors to measure the mass of materials being conveyed, but they often have accuracy problems due to the length, speed and tension in the conveyor belt.
It is a further problem of falling-stream samplers that they require significant vertical space between the conveyor discharge point and any other structure to allow the falling-stream cutter to be placed and to move. Due to this height requirement, it is very difficult and expensive to retrofit falling-stream samplers into existing plants. They are often placed at a great height above loading bins or plant feed entry points causing problems with access and potential safety problems. It also means that often falling-stream samplers in these locations are not given the maintenance work that they should due to safety and access problems.
Falling-stream samplers also require that the conveyor be stopped whilst maintenance work is carried out and this interferes with production.